Based on lectures the author gave at various universities, this book is meant for persons interested in the history of modern and nuclear physics. Emilio Segrè, who received the 1954 Nobel Prize in Physics, attempts to describe this world as he would to a close friend in another field. He tries “to show not only the main discoveries but also the way they were reached, the personalities of the leading physicists, and the errors committed before the right path was found” (preface). The scientists highlighted include Henri Becquerel, Pierre and Marie Curie, Ernest Rutherford, Max Planck, Albert Einstein, Niels Bohr, Enrico Fermi, Ernest Lawrence, and some other lesser-known physicists. The book includes a broad bibliography.